This invention relates to an antenna, provided to a vehicle rear window glass, for transmitting and receiving ultrashort waves. The window glass is provided with defogging heater strips. The antenna is arranged in a space below the heater strips and constructed of a plurality of conductive strips attached to the window glass in a special pattern. The antenna is particularly suitable to mobile phones and/or personal radio transmitter-receivers installed on automobiles.
In current automobiles it is customary to use a pole antenna for the transmission and reception of ultrashort waves assigned to mobile phones and/or personal radios. However, the protrusion of a pole antenna from a car body is unfavorable for safety and also for good appearance of the car. Besides, pole antennas are obstructive to car washing and liable to break.
There are some proposals of providing an antenna for transmission and reception of ultrashort waves on an automobile window glass: for example, JP 62-69704 A and JP 62-26912 A (Utility Model). However, window glass antennas proposed until now are considerably low in transmission and reception gains compared with conventional pole antennas and hence cannot be put into practical use for car telephones or personal radios.
In the case of providing a window glass antenna for a mobile phone and/or a personal radio to an automobile rear window glass which is preferentially provided with defogging heater strips, it is usual to arrange the antenna within a space left below the heater strips, and according to general knowledge the window glass antenna needs to have a horizontally elongate element as an upper end part of the antenna. If that horizontal element of the antenna is close to the heater strip in the lowermost position, the influence of that heater strip on the horizontal antenna element causes lowering of the reception gain of the antenna, and hence it is desirable to keep a vertical distance of at least 40 mm between the horizontal antenna element and the lowermost heater strip. Actually, however, it is difficult to realize such spacing because, in order to secure the rear view of the driver, it is impermissible to reduce the defogging capability by enlarging the distance between the lowermost heater strip and the lower edge of the window glass.